Question

A car weighing 700 kgf changes its speed from 36 km/h to 72 km/h in 2 minutes. What is the work done by the engine? Consider $g=10m/s^2$

[1 mark]

• A. $1360.8\times {10}^{3}J$
• B. $1360.8\times {10}^{4}J$
• C. $105.00\times {10}^{3}J$
• D. $105.00\times {10}^{4}J$

Answer 1

The correct option is C $105.00\times {10}^{3}J$

Given,
Mass of the car = 700 kg
Initial speed = 36 km/h = 10 m/s
Final speed = 72 km/h = 20 m/s

Change in kinetic energy =
$\frac{1}{2}m{v_f}^2-\frac{1}{2}m{v_i}^2=\frac{1}{2}m({20}^2-{10}^2)J$

Using work energy theorem,

⇒ Work done by the engine = Change in the kinetic energy of the car
⇒ Work done by the engine =$\frac{1}{2}m({20}^2-{10}^2)J=105.00\times {10}^{3}J$